At its most fundamental level, our Will is divine and therefore harmonises with our divine destiny - our true Will is therefore something we can be true-to, or false-to; but the true Will is not something we can choose or command.
Furthermore, for most people (not everybody) our strongest experience of beauty is related to love and the opposite sex - hence (for Christians) with marriage. This combination of factors raises the possibility that the right marriage partner for us (that is, our soulmate) will one day arrive in our vicinity.
This would not be an accident; but the result of exactly that same divine power which is causing us to know ourselves via our experiences in this world. The right partner in marriage is the best possible experience we can have of our unconscious and unrealised nature.
Such a partner may well be chosen, but in our pre-mortal spirit life; as a major element of our destined experiences.
(Such experiences may be destined - however, our response to experience is not destined; since we are free-agents.)
The physical aspects, emotions, desires, aspirations of sex can be seen as the true Will working through at many levels through mortal experience. And sex is extremely complex and far-reaching, since it represents destined purposes and desires that our conscious personality may know little or nothing about.
The power of sex is therefore the power of Will; and therefore not subject to our choice - we cannot decide to fall in love; we can only decide whether to live truly by love, when it happens, or not.
And this is a part of the decision whether to live truly by everything, or not.
And this is to be true to our real-Self, or not.
Paraphrased and adapted to express my own views more exactly, from William Arkle's A Geography of Consciousness (1974) - mostly the chapter Beauty, plus elements of the chapter Will.